converting a combi to a system boiler

twodds · Mar 5, 2015

Hi Chaps
im working o a combi boiler that has been converted to a system boiler,the combi has a 2 channel time clock and we are installing a tank and s plan has anybody got any info what to do with the combi wiring.thought this would be easy but ive been told its a tad difficult.cheers twodds

marc8 · Mar 5, 2015

Well I was looking at doing my Combi as I am solar PV installer & want unvented cylinder installed with twin coil this way can have solar thermal & solar PV & install proportional heating controller.
The way I was going to do this was to install 2 motorised valves s plan layout one for heating one for hot water, this would make the combi into two heating zones but using one zone for hot water side (indirect cylinder).
This way valve would be controlled via the cylinder stat & if required but not sure till I installed it to see what would happen I could install 2 small relays & go through each coil so other would not work whilst other was on.
Have done something similar with a swimming pool as we had 2 pumps on the system & boiler running through a heat exchanger,
if one relay was in this would cut the power to the other coil, but also the other would not cut in until the first engaged was satisfied.
I would then install my 3rd heating zone which do my underfloor heating in the kitchen this would go through heat exchanger unit so when hot water is satisfied it would divert to underfloor heating if required from the heating controller or boiler, complex but I like heating & puzzles like that.
Hope the aboves makes sense?
But mine would only be until my combi was laid to rest then I would do this all through systems boiler.

LankyWill · Mar 5, 2015

What programmers are you using? Is the cylinder pre wired? Is it in close proximity to combi boiler? A bit more info is needed.

TJ Anderson · Mar 5, 2015

twodds said:
Hi Chaps
im working o a combi boiler that has been converted to a system boiler,the combi has a 2 channel time clock and we are installing a tank and s plan has anybody got any info what to do with the combi wiring.thought this would be easy but ive been told its a tad difficult.cheers twodds

Very, very easy if you do heating controls. You wire S plan exactly as you would for system boiler. Basically the combi has a switched live for demand the same as system boiler, the combi hot water is controlled automatically when water is drawn off.The plumbing will alter so that hot water to taps is from a cylinder not from combi but the plumber will sort that when he installs cylinder. It is also quite common in larger houses to have a combi boiler with S Plan. Water cylinder HW for bathrooms and using the combi HW for kitchen and utility.

Leesparkykent · Mar 5, 2015

What's difficult about it? It's an s plan with the pump integral to the boiler. Look at the manufacturers instructions it will have typical drawings to follow. Most state that all controls must be protected by the boilers internal fuse, so you wire the feed for the boiler from the FCU and feed the controls from the output on the boiler. For example most Worcesters the controls would be fed from LS and the oranges would be connected to LR.

LankyWill · Mar 5, 2015

How many zones are you having? One or two? Wiring is easy, just wire, single core, 1mm, 3-core from boiler to joint. then wire one roomstat to boiler and one to joint(3-core). Most new cylinders have hot water valve and cylinder stat pre wired.

twodds · Mar 5, 2015

Hi Chaps
ok on the boiler the 2 channel timer is wired as a plug into the with centre as L/N/E and ch /hw
can I wire as from a different programmer take my orange from my 2 ports and use them as my c/h and h/w back to the boiler centre,ive done this and it worked but after awhile it stopped working ?

LankyWill · Mar 5, 2015

That's because the circulator didn't have anything calling for it. Does this new system have a cylinder? If so what components are on it?

Leesparkykent · Mar 5, 2015

twodds said:
Hi Chaps
ok on the boiler the 2 channel timer is wired as a plug into the with centre as L/N/E and ch /hw
can I wire as from a different programmer take my orange from my 2 ports and use them as my c/h and h/w back to the boiler centre,ive done this and it worked but after awhile it stopped working ?

http://www.worcester-bosch.co.uk/cache/file/482/gas-boiler-wiring-guide.pdf

page 29 will give you an idea. This is obviously for a Worcester system boiler but the principals are the same. What make is the boiler you are doing?

Leesparkykent · Mar 5, 2015

......

telectrix · Mar 5, 2015

you could always get geordie spark over to wire it up but by the time he's done it, tidyboiler will have nicked all the copper pipework.

Geordie Spark · Mar 5, 2015

telectrix said:
you could always get geordie spark over to wire it up but by the time he's done it, tidyboiler will have nicked all the copper pipework.

Bog off!!

I've been watching this thread with interest from a very safe distance and intend to keep it that way!!

Tidyboiler at this moment is sprawled on my settee snoring like a pig.

She's not been well these past few weeks but is a lot better now.

telectrix · Mar 5, 2015

dreaming of rolls of solid drawn 240mm copper no doubt

twodds · Mar 5, 2015

Yep they've put a tank next to the boiler and capped the water pipes

Leesparkykent · Mar 5, 2015

twodds said:
Yep they've put a tank next to the boiler and capped the water pipes

Do you get the wiring now?

converting a combi to a system boiler

twodds

marc8

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LankyWill

TJ Anderson

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Leesparkykent

LankyWill

twodds

LankyWill

Leesparkykent

Leesparkykent

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telectrix

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